FACTBOX: Developments in Kenya crisis on Jan 29

(Reuters) - Kenyan military helicopters swooped over machete-wielding crowds on Tuesday against a backdrop of spiraling tribal violence after a disputed election.

Around 850 people have been killed since the December election which kept President Mwai Kibaki in power but which opposition leader Raila Odinga says was rigged.

Following are developments in Kenya at 6:20 a.m. EST on Tuesday.

NAIVASHA - Helicopters dive-bombed a crowd, firing what police said were rubber bullets at a mob of about 600 people brandishing machetes and clubs at members of another tribe.

NAIROBI - Kibaki appealed to all Kenyans to maintain peace. Odinga warned that Kenya was drifting into anarchy.

NAIROBI - Melitus Were, newly elected member of parliament for Odinga's Orange Democratic Movement (ODM), was shot dead near his house shortly after midnight.

NAIROBI - Fresh ethnic violence broke out in Nairobi's Kibera slum after the opposition politician was killed. At least seven people were killed.

RIFT VALLEY - Mobs ransacked homes, burning belongings and threatening people trying to flee Naivasha. Nearly 100 people have died in recent days in the Rift Valley.

KISUMU - Protests rocked Kisumu on Monday. Police fired in the air and one demonstrator died, residents said.

UNITED NATIONS - U.N. special adviser on preventing genocide, Francis Deng, has warned Kenyan politicians they could be held responsible for crimes against international law.

NAIROBI - A spokesman for former U.N. head Kofi Annan, attempting to mediate between Kibaki and Odinga, said negotiating teams would begin "formal dialogue" on Tuesday afternoon.

NAIROBI - Stock exchange halted trade for a few minutes as the index fell 5 percent in accordance to trading rules. Kenya's shilling was near a 3-year low versus the dollar.

(Writing by David Cutler, London Editorial Reference Unit; Editing by Matthew Tostevin)